I played WC3 extensively back in the days.
Bnet is controlled very well. I hardly doubt any kind of blatant cheats exist because most of the gameplay info is sent from server-side.
There aren't any resource hacks, I'm sure. It's near impossible. Only maphacks exist which exploits the client-side data.
To be frank, lots of people on ATOT aren't good at competitive RTS- older demographics + even an older game.
It's possible you just aren't good and he just outplayed/macro/micro'd you- especially if you don't have a good grasp of the game where you're not 'sure' if he's hacking. He probably had a third expansion somewhere.
Why don't you watch the replay?